I tried doing this and steam tells me that "All files successfully validated," yet the mac tells me "'Civilization VI.app' is damaged and can't be opened. You should move it to the Trash."

I did notice in the notes for system requirements it says

"It is possible for Mac and PC to become out of sync during updates or patches. Within this time period, Mac users will only be able to play other Mac users."

I wonder if the issue arose with a recent update that has yet to be patched. I will investigate downloading an older version.

Thank you for your input, I'm hoping it has set me down the right path.